Hundreds of thousands are expected to march in May Day protests in cities across the U.S. Monday, many of them in opposition to President Donald Trump’s immigration policies, days after the president celebrated the effects of those policies at a rally marking his 100th day in office.

“In just 100 days, we have taken historic steps to secure our border, impose needed immigration control like you’ve never seen before, is that true? And properly screen and vet those seeking admission into our country,” Trump told a crowd of supporters in Harrisburg, Pennsylvania on Saturday night. “Our immigration system should put the needs of American workers, American families, American companies and American citizens first.”

Organizations that advocate for immigrants, both documented and undocumented, said they were taking to the streets Monday to counter Trump’s narrative that foreigners are responsible for the nation’s problems.

“May 1 is a day where we lift up the voices of immigrant workers and their families,” said Angelica Salas, executive director of the Coalition for Humane Immigrant Rights (CHIRLA), which planned a march in Los Angeles with tens of thousands of people.

Salas accused the president of pursuing an agenda that punishes immigrants and the communities that support them.

“It is not fair, it is not right to continue to attack immigrants in the way that Donald Trump has,” she said.

“Whether you agree with Trump’s proposed solution or not, we can all agree that he is failing us currently to provide and promote smart immigration reform for all,” he said.

In the early weeks of his presidency, Trump signed executive orders to step up immigration enforcement at the border and within the country. He has solicited bids from contractors to build a wall on the southern border, though many in Congress have resisted appropriating funds for it.

Another order that would have temporarily banned immigration from several Muslim-majority countries and halted acceptance of refugees remains held up in court. States have also filed legal challenges against an order to withhold some federal funding from cities that refuse to cooperate with immigration authorities.

“We are coming together today to send a message across the country and the globe that we need our elected leaders to understand that scapegoating immigrants is not the answer to a more prosperous country, but divides us,” Sanchez said.

The long-term goal is a path to citizenship for the estimated 11 million undocumented immigrants in the U.S., but with Trump in the White House and Republicans controlling Congress, activists are mainly looking for strength and solidarity from Democrats.

“I want our members of Congress to have courage,” Salas said. “These are very difficult times. We do have a bully in the White House.”

Democrats are displaying some signs of resolve. On ABC’s “This Week” Sunday, House Minority Leader Nancy Pelosi dismissed the possibility of a “grand bargain” with Trump where Democrats support funding for a border wall in exchange for legal status for the undocumented.

“We don’t have to pay for us to do the right thing as a country,” she said. “And overwhelmingly, the American people support a path to citizenship, for the people who are in our country. We have to protect our borders; that is our responsibility as a nation, north and south.”

Sanchez said Democrats should continue fighting for common sense immigration reform that reduces both the exploitation of immigrant workers and the incentives for employers to hire undocumented immigrants.

“In the minority, Democrats in Congress should remain steadfast in opposing solutions that run counter to this vision,” he said.

While protesters are outraged by the president’s handling of the issue so far, anti-illegal immigration groups are cautiously optimistic.

“These actions taken by the administration during the first 100 days represent a positive start to the long process of reforming our nation’s immigration policies so that they best serve the interests of the American people,” Dan Stein, president of the Federation of Americans for Immigration Reform (FAIR), said in a statement last week.

According to Ira Mehlman, media director for FAIR, Trump has proven that the notion of illegal immigration as an intractable problem is wrong.

“The most important thing he has done is he has changed perceptions,” he said in an interview Monday.

Mehlman pointed to the drop in border crossings to 17-year lows and a massive reduction in unaccompanied minors attempting to enter illegally, apparently driven by the expectation of tougher enforcement of immigration laws.

“Just demonstrating a little bit of resolve has enormous impact,” he said.

The Center for Immigration Studies has also praised Trump’s initial work on immigration, saying he has made significant progress in reversing “the Obama administration’s eight-year history of deliberately ruinous immigration policies.”

Still, even those who support the direction of Trump’s immigration agenda have concerns.

“Where he’s come up short is failing to press Congress to enact any kind of meaningful legislation,” Mehlman said.

He noted that the reported congressional agreement to continue funding the government discards many of Trump’s priorities on immigration, including the border wall.

“They continue to back away from any meaningful action on immigration enforcement,” he said.

In the absence of cooperation with Congress, Trump has acted mainly through executive orders, and most of what he has done has been about enforcing the laws already on the books rather than making new immigration policies. In the remainder of Trump’s term, Mehlman said FAIR hopes to see “continued resolve in enforcing immigration laws plus putting pressure on Republican leadership in Congress to do its job.”

He sees potential for some common ground with Democrats on issues like E-Verify. Pelosi and other party leaders may be adamantly opposed to compromise, but there are 10 senators up for reelection in 2018 in states that Trump won who may be more pliable.

Mehlman suggested Trump may try to use President Obama’s Deferred Action for Childhood Arrivals program as a bargaining chip with Democrats. The administration has sent mixed messages about undocumented immigrants protected by program, known as “Dreamers.”

Trump himself has repeatedly insisted that Dreamers do not need to fear deportation, and USCIS has continued approving and renewing applications. However, Attorney General Jeff Sessions has made clear that anyone in the country illegally is subject to removal.

“We can’t promise people who are here unlawfully that they’re not going to be deported,” Sessions told Fox News last month.

Homeland Security Secretary John Kelly echoed Trump’s position to CNN recently, saying of Dreamers, "We're not targeting them. The President obviously is sympathetic. But I just wish these kind of issues were dealt with legally by the United States Congress.”

One man has filed a lawsuit claiming he was deported despite DACA status, but DHS maintains Juan Manuel Montes Bojorquez left the country without authorization and voided his protection.

“I think it’s safe to say that given some of President Trump’s early actions in office, his campaign promises, and conflicting statements around deportation and DACA, the integrity of the government’s promises are truly at stake,” Sanchez said.

May Day demonstrations have a long history in the U.S. and around the world, commonly focused on workers’ rights and labor issues. In recent decades, U.S. protests have shifted toward advocacy for immigration reform and protecting immigrant workers.

In 2006, massive crowds took to the streets to oppose controversial federal immigration legislation. Attendance for May Day protests has dipped since then, but Trump’s election has inspired a surge of activism on the left that will likely reverse that trend.

Organizers say this year’s protests are about more than immigration, as various causes that oppose Trump come together in resistance. According to Salas, CHIRLA is being joined by groups representing women’s rights, the African American community, LGBTQ equality, environmentalism, and labor.

The protests come two days after marches for climate change in several major cities, and they follow months of large, passionate displays of opposition to Trump from the progressive movement.

Mehlman warned the demonstrations could backfire and rile up more support for Trump.

“I think it’s just going to increase the resolve of the American people that immigration laws exist for a reason and we have to enforce them,” he said.

Police departments in many cities have braced for potential unrest either during or after the protests. May Day protests in Seattle in 2016 devolved into chaos with rocks and Molotov cocktails hurled at officers and nine people arrested.

There have been some tense confrontations so far on Monday, but organizers insist their intent is to hold a nonviolent demonstration.

“We want our streets to be a place of safety for all,” Salas said.

CHIRLA is working closely with the Los Angeles Police Department to avoid violence, and the group has emphasized to marchers that they must be disciplined and peaceful.

“Today is a day of unity,” she said. “Today is a day to put forward a vision of America, of a united force.”